1. Field of the Invention
The present invention relates to an outboard motor.
2. Description of the Related Art
Outboard motors provided with a catalyst to clean the exhaust from the engine are known. For example, in the outboard motor disclosed in U.S. Pat. No. 5,554,057, a catalyst is disposed below the engine. It is disclosed that water is kept out of the catalyst by disposing a heat accumulator downstream of the catalyst.
In U.S. Pat. No. 7,698,889, which relates to a stern drive rather than an outboard motor, it is disclosed that water is kept out of the catalyst by disposing a non-catalytic porous member downstream of the catalyst.
In the outboard motor disclosed in U.S. Patent Application Publication 2009/0215341, an exhaust pipe extends upward from a cylinder, passes above the cylinder, and extends downward at the opposite side of the cylinder. A moisture capture member is disposed in a portion of the exhaust pipe. The portion is positioned above the cylinder.
In the outboard motor of U.S. Pat. No. 5,554,057 referred to above, the catalyst and the heat accumulator are disposed in a position near the water surface. Because of this, the possibility of the catalyst and the heat accumulator becoming wet is high. When the catalyst becomes wet, there is a possibility that the exhaust cleaning function of the catalyst will be degraded. The cleaning function of the catalyst may also be degraded by substances in the exhaust. For example, phosphorus contained in the engine oil flows together with the exhaust and is deposited in the catalyst, whereby the cleaning function of the catalyst may be degraded.
The motor disclosed in U.S. Pat. No. 7,698,889 is astern drive that includes an engine disposed on-board, rather than an outboard motor. Because of this, an exhaust pipe extends above the engine. Consequently, the catalyst is disposed above the engine, and the moisture capture member is disposed even further above the engine and the catalyst. In cases in which this kind of structure is applied in outboard motors, there is the possibility that if water passes through the moisture capture member, the water will reach all the way to the engine, and not merely the catalyst.
In the outboard motor of U.S. Patent Application Publication 2009/0215341, an exhaust pipe passes above a cylinder, and a moisture capture member is disposed in the section that has the highest position in the exhaust pipe. However, the top cover of the outboard motor houses the engine, and the space inside the top cover is therefore limited. Because of this, the layout of an exhaust pipe such as that of the outboard motor of U.S. Patent Application Publication 2009/0215341 is difficult to achieve without increasing the size of the outboard motor.